In order to obtain an official approval, internal combustion engines, particularly spark ignition engines and diesel engines, have to comply with certain emission standards or emission laws such as, for example, regulation (EC) 692/2008. Standards associated with regulations such as this specify certain emission limits, in particular, for carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons (HC), particle mass (PM) and particle number (PN) for the particular jurisdiction such as member states of the European Union. In addition to the emission limits, the emission standards typically specify the test conditions under which the emission characteristics of the respective internal combustion engine have to be analyzed. Depending on the particular standard that applies to an internal combustion engine to be analyzed, static or dynamic driving states are analyzed on a roller-type dynamometer. For example, certain speed and acceleration profiles are driven and it is subsequently checked whether or not the emission values of the exhaust gases emitted by the analyzed internal combustion engine exceed the legally specified emission limits.
The dynamic test conditions, in particular, are intended to simulate the driving states occurring in the normal driving mode in order to analyze whether or not the internal combustion engine also complies with the emission limits in the normal driving mode. In order to ensure the reproducibility of the test results, the various standards specify the test conditions, under which the internal combustion engine has to be analyzed, in a relatively precise fashion. The currently valid test cycle for Europe is the NEDC (New European Driving Cycle), which specifies the test conditions to be analyzed. As a result, the engine manufacturers design the internal combustion engines in such a way that they comply with the emission limits in accordance with the NEDC. Although the NEDC also contains dynamic test conditions, the test conditions are known. It is particularly known, at which operating points the internal combustion engine is tested and how long and how often the internal combustion engine is at these operating points. In the NEDC, operating points in the lower part-load range of the internal combustion engine are also analyzed. Consequently, the NEDC and similar test cycles only simulate the normal driving mode of the internal combustion engine roughly at best such that internal combustion engines, which comply with the applicable European standards, sometimes significantly exceed the specified emission limits in the normal driving mode.
In order to minimize the variations between the emission characteristics of the respective internal combustion engine under test conditions and in the normal driving mode, the emission characteristics of internal combustion engines will in the future no longer or no longer only be analyzed on a roller-type dynamometer and in accordance with the NEDC, but rather on a conventional road-test route such that it can be subsequently determined if the emission values also comply with the emission limits under normal driving conditions. Such test methods are also referred to as RDE (“Real Driving Emissions”) methods, in which the internal combustion engine is not analyzed on the dynamometer, but rather in normal road traffic without prior knowledge of the road-test route to be used. The vehicle being analyzed carries along a corresponding emission analyzer (PEMS, portable emission measurement system). It is therefore also not known, at which operating points and under which ambient conditions such as, for example, the incline of the route traveled and the current weather conditions (e.g. wind and external temperature) the internal combustion engine is analyzed.
In order to also comply with the corresponding emission standards when the RDE test method is used, the internal combustion engine can be designed in such a way that it also complies with the emission limits under the most unfavorable boundary conditions (“worst-case scenario”) that can occur in the normal driving mode. An example of such unfavorable boundary conditions may be an acceleration maneuver on an incline in a headwind. In order to also comply with the emission limits under these boundary conditions, for example, the maximum power output of the internal combustion engine can be correspondingly limited in the first place. These and similar countermeasures, which are based on the “worst case scenario,” are also referred to as static calibrations and cannot be changed in the driving mode. In this context, it is disadvantageous, for example, that the power reserves of the internal combustion engine cannot be fully utilized although the “worst-case scenario” is an extremely rare occurrence and the internal combustion engine would not exceed the emission limits under more “mild” boundary conditions. Due to these static calibrations, the design of the internal combustion engine has to be permanently based on unfavorable boundary conditions that only occur very rarely.